dt-bindings: iio: pressure: add LPS22HH bindings

Fix following checkpatch warnings:
WARNING: DT compatible string "st,lps22hh" appears un-documented -- check ./Documentation/devicetree/bindings/
		.compatible = "st,lps22hh",

WARNING: DT compatible string "st,lps22hh" appears un-documented -- check ./Documentation/devicetree/bindings/
		.compatible = "st,lps22hh",

Fixes: e5aab7b0

 ("iio:st_pressure:initial lps22hh sensor support")
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>